1. Field of the Invention
This invention relates to a color copying apparatus, and more particularly to a color copying apparatus which uses one or more photosensitive mediums (screen-like photosensitive mediums) each have a plurality of small-diameter openings to enable good color representation to be accomplished.
2. Description of the Prior Art
Color copying apparatuses have generally given rise to various problems which would not be experienced in monochrome copying apparatuses for producing black-and-white copies. These problems include the problem of alignment for color resolution and exposure to a multi-color image, the problem of color mixture resulting from the use of multiple color developers, and the problem of offset which is a phenomenon that a color developer once transferred from a photosensitive medium to a recording medium is re-transferred to the photosensitive medium.
Various types of electrophotographic color copying apparatus have heretofore been proposed, but in the type of apparatus based on the Carlson process, for example, color mixture has readily occurred because various color developers are used on a photosensitive medium.
Also, in the apparatuses based on TESI process wherein transfer of latent image is effected, the possibility of developer being re-transferred to the photosensitive medium occurs during representation of a second or subsequent color, with a result that the final copy image might be degenerated in quality as has been experienced in the above-described apparatuses based on the Carlson process.
In these apparatuses wherein a transfer medium is brought into direct contact with a photosensitive medium, the transfer medium is apt to be misaligned with respect to the photosensitive medium and this may lead to the probability that resultant copies may misregister.
U.S. Pat. No. 3,532,422, issued to S.B. McFarlane Oct. 6, 1970, discloses an apparatus in which a color image may be formed without the copy medium being brought into direct contact with a photosensitive medium. According to this patent, a photosensitive medium comprising a mesh-like metal grid covered with a photoconductive member is electrostatically charged and exposed to image light, whereafter a formed electrostatic latent image is developed by means of a predetermined color developer, and then the developer image is transferred to transfer paper disposed with an air space with respect to the photosensitive medium.
Such apparatus is not subject to the possibility of the transfer paper being misaligned and does not require any complicated mechanism for ensuring the registration, but due to the grid-like configuration of the photosensitive medium, difficulties might be encountered in satisfactorily removing the once used developer from the photosensitive medium, thus resulting in color mixture in the final copy.